| 摘要 |
PURPOSE:To obtain images of good quality even in case of a secular change by varying and setting the clamp levels of black fixing circuits for B and R on the basis of an initial set value G. CONSTITUTION:A reference voltage generating circuit 7 outputs a voltage (reference voltage) equal to the output level of a black detecting circuit 3G for G in an initial state where there is no secular change. The reference voltage generated by the reference voltage generating circuit 7 is compared with the output voltage of the black detecting circuit 3G by a comparing circuit 43 to generate a comparison error voltage, which is AD-converted by an AD converter 53 and supplies to an amplifier 6G, whose gain is varied so that the output level of the comparing circuit 43 is zero, thus varying and setting the clamp level of the black fixing circuit 2G' for G. Consequently, the black level of G is set to said initial value even if the output of a television camera has a secular change. |
